Polymer electrolyte fuel cell

ABSTRACT

A polymer electrolyte fuel cell shall be provided such that degradation of the fuel cell due to condensed water can be prevented. A polymer electrolyte fuel cell of the present invention is provided wherein a plate A, a plate B, and a plate C are used; a passage is formed on each of the front and rear sides of each of the above-mentioned plates; a cell D or a permeable film E is interposed between two of the above-mentioned plates; a cell unit is thus formed; a plurality of such cell units are integrally laminated to form a polymer electrolyte fuel cell. Fuel gas and cooling water are caused to flow into a humidifying chamber F to humidify fuel gas. The resulting humidified fuel gas is supplied to a fuel chamber G, and moreover, oxidant gas is supplied to an oxidant chamber, thereby generating electricity. It is so arranged that the flow of fuel gas moving inside the above-mentioned humidifying chamber F is a counter flow with respect to the flow of cooling water moving inside the above-mentioned humidifying chamber F; and the flow of fuel gas moving inside the above-mentioned fuel chamber G is a co-flow with respect to the flow of cooling water moving inside the above-mentioned fuel chamber G.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a polymer electrolyte fuel celland more specifically, to the polymer electrolyte fuel cell whosepassage is prevented from being blocked by condensed water.

[0003] 2. Detailed Description of the Prior Art

[0004] A polymer electrolyte fuel cell is basically so arranged that ananode and a cathode are provided, with an electrolytic polymerelectrolyte film interposed in-between; a fuel gas containing hydrogenis caused to flow on the anode side; and an oxidant gas containingoxygen is caused to flow on the cathode side; thereby generatingelectricity and water through electrochemical reaction.

[0005] In this arrangement, cooled water is supplied to humidify fuelgas or oxidant gas for the purpose of enhancing the electricconductivity of the polymer electrolyte membrane. The resultinghumidification not only causes the polymer electrolyte membrane to bewetted but also lowers the heat generated by the exothermic reaction ofthe fuel cell.

[0006]FIG. 8 shows an example of a prior art polymer electrolyte fuelcell wherein:

[0007] a plate A, a plate B, and a plate C are used;

[0008] a cell D is disposed on the front side of the plate A;

[0009] another cell D is disposed on the rear side of the plate A;

[0010] a permeable film E is disposed on the rear side of the plate B(on the other side than that side of the plate B which is opposite acell D);

[0011] another permeable film E is disposed on the front side of theplate C (on the other side than that side of the plate C which isopposite a cell D);

[0012] a cell unit is thus formed;

[0013] a plurality of such cell units are integrally stacked to form apolymer electrolyte fuel cell; and

[0014] a humidifying chamber F is provided between two adjacent cellunits, namely between the plate C and a plate (B).

[0015] A passage is formed on each of the front and rear sides of eachof the plates A, B, and C (A″, B″, and C″ denote the rear side of theplate A, the rear side of the plate B, and the rear side of the plate C,respectively). Fuel gas, which is supplied from a lateral portion of thepolymer electrolyte fuel cell, flows in through a fuel inlet B1, and isdischarged through a fuel outlet B2 after passing through a fuel chamberdisposed on the anode side of each of the cells D. Oxidant gas flows inthrough an oxidant inlet B3, and is discharged through an oxidant outletB4 after passing through an oxidant chamber disposed on the cathode sideof each of the cells D. Furthermore, cooling water flows in through acooling water inlet B5, and is discharged through a cooling water outletB5 after passing through a humidifying chamber F (disposed on the rearside of the plate B). In this arrangement, fuel gas is humidified bycooling water in the humidifying chamber F, and the polymer electrolytemembrane placed in the center of each cell D is humidified by theresulting humidified fuel gas. FIG. 9 shows a schematic diagram showingflows of fuel gas, of oxidant gas, and of cooling water.

[0016] In the case of the above-described polymer electrolyte fuel cell,the flow of fuel gas moving inside the humidifying chamber F is aco-flow with respect to the flow of cooling water moving inside thehumidifying chamber F, and the flow of fuel gas moving inside the fuelchamber is a counter flow with respect to the flow of cooling watermoving inside the fuel chamber, where the term co-flow signifies a flowin the same direction, and the term counter flow signifies a flow in theopposite direction (the same definitions apply hereinafter), providedthat a direction of a flow is not limited to a vertical direction butmay include a somewhat oblique direction and a horizontal direction, aswell as a direction along a bent or otherwise irregular line, inconsideration of the fact that passages have various configurations.

[0017] As described above, in the case of a polymer electrolyte fuelcell, electrochemical reaction accompanied by exothermic reaction takesplace, and therefore, the temperature of that portion of each platewhich faces one of the cells D becomes higher than that of the exteriorperiphery of the cell D. In the event that fuel gas is humidified by soarranging that the flow of fuel gas is a co-flow with respect to theflow of cooling water as mentioned above, then in the humidifyingchamber, the temperature of cooling water at the outlet becomes higherthan that at the inlet, and therefore it is possible to obtain saturatedhumidified fuel gas which has a high temperature (equivalent to thetemperature of that portion of the cells D which has the highesttemperature).

[0018] However, as can be seen from FIGS. 10(a) and (b), the temperatureof that portion of the humidifying chamber F which is in theneighborhood of the humidified fuel gas outlet is 2 to 3° C. lower thanthat of humidified fuel gas, and therefore, the water content in thehumidified fuel gas is condensed. In the event that condensed water isgenerated, then fuel gas is hindered from flowing, resulting in the fuelcell performance being degraded. Furthermore, if it is so arranged thatthe flow of fuel gas moving inside the fuel chamber is a counter flowwith respect to the flow of cooling water moving inside the fuelchamber, then the temperature at the outlet of the fuel chamber becomeslower than that at the inlet thereof. In the event that the temperatureat the outlet of the fuel chamber lowers, then the water content in fuelgas becomes prone to be condensed, owing also to the fact that fuel gasis consumed at the outlet of the fuel chamber, thereby causing the fuelgas velocity to increase. The resulting condensed water hinders fuel gasfrom flowing, thereby causing the fuel cell performance to be degraded.Moreover, water is generated owing to reaction on the cathode side. Inaddition to humidification water, the resulting generated waterconstitutes still another factor for water condensation. This phenomenoncan be prevented by reducing the utilization ratio of fuel or ofoxidant, thereby increasing the fuel gas velocity at the fuel chamberoutlet, but this practice is undesirable in terms of the fuel cellefficiency.

SUMMARY OF THE INVENTION

[0019] It is an object of the present invention, which was made for thepurpose. of solving the problem of water being condensed in prior artpolymer electrolyte fuel cells, is to provide a polymer electrolyte fuelcell wherein the directions of flows of fuel gas, of oxidant gas, and ofcooling water are suitably combined, thereby enabling water condensationto be prevented.

[0020] By way of a means for achieving the above-mentioned object, thepolymer electrolyte fuel cell of the present invention is so arrangedthat

[0021] a polymer electrolyte membrane having an anode on one side and acathode on the other side constitutes a cell;

[0022] a fuel chamber with fuel gas flowing inside is provided on theanode side of the above-mentioned cell;

[0023] an oxidant chamber with oxidant gas flowing inside is provided onthe cathode side of the above-mentioned cell;

[0024] the above-mentioned cell, the above-mentioned fuel chamber, andthe above-mentioned oxidant chamber constitute a component cell;

[0025] a plurality of such component cells are laminated together toconstitute a cell unit;

[0026] a plurality of such cell units are provided;

[0027] a humidifying chamber with cooling water flowing inside isprovided between two adjacent cell units, thereby humidifying eitherfuel gas or oxidant gas, or both fuel gas and oxidant gas; and

[0028] the flow of fuel gas moving inside the above-mentioned fuelchamber, as well as the flow of oxidant gas moving inside theabove-mentioned oxidant chamber, is a co-flow with respect to the flowof cooling water moving inside the above-mentioned humidifying chamber.

[0029] Furthermore, the above-mentioned polymer electrolyte fuel cell isso arranged that

[0030] the flow of fuel gas moving inside the above-mentionedhumidifying chamber is a counter flow with respect to the flow ofcooling water moving inside the above-mentioned humidifying chamber; and

[0031] the flow of fuel gas moving inside the above-mentioned fuelchamber is a co-flow with respect to the flow of cooling water movinginside the above-mentioned fuel chamber.

[0032] Moreover, in the above-mentioned polymer electrolyte fuel cell,fuel gas and oxidant gas are replaced with each other, thereby causingoxidant gas to be humidified in the humidifying chamber.

[0033] If it is so arranged that the flow of fuel gas moving inside thefuel chamber, as well as the flow of the oxidant gas moving inside theoxidant chamber, is a co-flow with respect to the flow of cooling watermoving inside the humidifying chamber, then the resulting cooling wateris used to cool the heat generated in the cells, and therefore, thetemperature of cooling water at the outlet becomes higher than that atthe inlet.

[0034] The temperature of the fuel gas or of the oxidant gas at theoutlet of the fuel chamber or of the oxidant chamber, respectively,becomes higher than the temperature of the fuel gas or of the oxidantgas at the inlet of the fuel chamber or of the oxidant chamber,respectively, since the flow of fuel gas moving inside the fuel chamber,as well as the flow of the oxidant gas moving inside the oxidantchamber, is a co-flow with respect to the flow of cooling water movinginside the humidifying chamber. For this reason, fuel gas or oxidant gasis consumed at the outlet of the fuel chamber or of the oxidant chamber,respectively, and therefore, water condensation which would be caused byreduced flow velocity can be prevented.

[0035] In the event that a polymer electrolyte fuel cell is so arrangedthat the flow of fuel gas moving inside the humidifying chamber is acounter flow with respect to the flow of cooling water moving inside thehumidifying chamber, and the flow of fuel gas moving inside the fuelchamber is a co-flow with respect to the flow of cooling water movinginside the fuel chamber; then the resulting cooling water is used tocool the heat generated in the cells, and therefore, the temperature ofcooling water supplied is bound to be lower (by 5 to 20° C.) than thatof the cells. Since the flow of fuel gas moving inside the humidifyingchamber is a counter flow with respect to the flow of cooling watermoving inside the humidifying chamber, saturated humidified fuel gas canbe obtained from the humidifying chamber such that the temperature ofthe above-mentioned fuel gas is lower than the temperatures of the cellsand than the temperature of a portion in the neighborhood of thehumidified fuel gas outlet. For this reason, humidified fuel gas can besupplied to the fuel chamber without causing any water content in thehumidified fuel gas to be condensed.

[0036] Furthermore, since the flow of fuel gas moving inside the fuelchamber is a co-flow with respect to the flow of cooling water movinginside the fuel chamber is a co-flow with respect to the flow of coolingwater moving inside the fuel chamber, the temperature of the fuel gas atthe outlet of the fuel chamber becomes higher than the temperature ofthe fuel gas at the inlet of the fuel chamber. For this reason, fuel gasis consumed at the outlet of the fuel chamber, and therefore watercondensation which would be caused by reduced flow velocity can beprevented.

[0037] In this connection, if it is so arranged that the flow of oxidantgas moving inside the oxidant chamber is a co-flow with respect to theflow of cooling water moving inside the oxidant chamber, then thetemperature at the outlet of the fuel chamber becomes higher, andtherefore, it is possible to increase the fuel utilization ratio whilepreventing water from being condensed at the outlet of the fuel chamber.

[0038] In the case of the polymer electrolyte fuel cell according to thepresent invention, the same results as above can be obtained in theevent that the flow of fuel gas and the flow of oxidant gas are replacedwith each other, thereby humidifying oxidant gas.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1 is an exploded perspective view showing major portions ofthe first embodiment of the polymer electrolyte fuel cell of the presentinvention.

[0040]FIG. 2 is an explanatory drawing schematically showing flows offuel gas, of oxidant gas, and of cooling water, in the above-mentionedfirst embodiment of the polymer electrolyte fuel cell.

[0041]FIG. 3(a) is an explanatory drawing showing the results ofmeasurements of temperatures in a humidifying chamber.

[0042]FIG. 3(b) is a diagram showing temperature distributions on apermeable film.

[0043]FIG. 4 is an exploded perspective view showing major portions ofthe second embodiment of the polymer electrolyte fuel cell of thepresent invention.

[0044]FIG. 5 is an explanatory drawing schematically showing flows offuel gas, of oxidant gas, and of cooling water, in the above-mentionedsecond embodiment of the polymer electrolyte fuel cell.

[0045]FIG. 6(a) is an explanatory drawing showing the results ofmeasurements of temperatures in a humidifying chamber.

[0046]FIG. 6(b) is a diagram showing temperature distributions on apermeable film.

[0047]FIG. 7 is a graph showing the results of an experiment conductedto determine relationships between fuel utilization ratios and cellvoltages.

[0048]FIG. 8 is an exploded perspective view showing major portions of aprior art polymer electrolyte fuel cell.

[0049]FIG. 9 is an explanatory drawing schematically showing flows offuel gas, of oxidant gas, and of cooling water.

[0050]FIG. 10(a) is an explanatory drawing showing the results ofmeasurements of temperatures in a humidifying chamber.

[0051]FIG. 10(b) is a diagram showing temperature distributions on apermeable film.

DETAILD DESCRIPTION OF THE PREFERRED EMBODIMENT

[0052] In the next place, the first embodiment of the polymerelectrolyte fuel cell of the present invention will be described on thebasis of attached drawings. The component members of this embodiment,which are the same as those of the above-mentioned prior art example,are represented by the same symbols that are used for those of theabove-mentioned prior art fuel cell.

[0053]FIG. 1 shows a polymer electrolyte fuel cell wherein

[0054] a plate A, a plate B, and a plate C are used;

[0055] a passage is formed on each of the front and rear sides of eachof the plates A, B, and C (A″, B″, and C″ denote the rear side of theplate A, the rear side of the plate B, and the rear side of the plate C,respectively);

[0056] a cell D is disposed between the plate A and the plate B;

[0057] another cell D is disposed between the plate A and the plate C;

[0058] a permeable film E is disposed on the rear side of the plate B;

[0059] another permeable film E is disposed on the front side of theplate C;

[0060] a cell unit is thus formed; and

[0061] a plurality of such cell units are integrally laminated to form apolymer electrolyte fuel cell.

[0062] A plate (B) of an adjacent cell unit is located on the front sideof the place C, and a humidifying chamber F is formed in such a way thatthe above-mentioned permeable film E disposed on the front side of theplate C is interposed between the above-mentioned plate (B) and theabove-mentioned plate C.

[0063] Furthermore:

[0064] the anode side of the above-mentioned cell D disposed between theplate A and the plate C faces the front side of the plate A;

[0065] the anode side of the above-mentioned cell D disposed between theplate A and the plate B faces the front side of the plate B;

[0066] a fuel chamber G is formed on the front side of the plates A;

[0067] another fuel chamber G is formed on the front side of the platesB;

[0068] the cathode side of the above-mentioned cell D disposed betweenthe plate A and the plate B faces the rear side of the plate A;

[0069] the cathode side of the above-mentioned cell D disposed betweenthe plate A and the plate C faces the rear side of the plate C;

[0070] an oxidant chamber H is formed on the rear side of the plate A(on the side A″); and

[0071] another oxidant chamber H is formed on the rear side of the plateC (on the side C″).

[0072] A fuel gas inlet a fuel gas outlet, an oxidant gas outlet, anoxidant gas inlet, an oxidant gas outlet, a cooling water inlet, and acooling water outlet are formed on each plate. On the plate (B) of theadjacent cell unit are also formed a fuel inlet B1, a fuel outlet B2, anoxidant inlet B3, an oxidant outlet B4, a cooling water inlet B5, and acooling water outlet B6. In this arrangement, however, the locations ofthe inlets and the outlets for oxidant gas and for cooling water arereverse to those in the prior art example.

[0073] In this arrangement, fuel gas flows in through the fuel inlet B1on the adjacent plate (B) and flows upward from the lower portion of thehumidifying chamber F through a passage on the rear side of the plate C.Cooling water which flows in through the cooling water inlet B5 on thelate (B) passes through the cooling water passage on each of the platesC, A, and B, and flows downward through the passage on the rear side ofthe plate B. Cooling water also flows downward through the passage onthe rear side of the adjacent plate (B); namely, cooling water flowsinside the humidifying chamber F, with the result that inside thehumidifying chamber F, the flow of fuel gas is a counter flow withrespect to the flow of cooling water. In this arrangement, a permeablefilm E exists between the plate (B) and the plate C as mentioned above,and therefore, as shown in FIG. 2, part of the cooling water flowingthrough the passage on the rear side of the plate (B) moves to the frontside of the plate C, and cools unhumidified fuel gas flowing through apassage on the front side of the plate C. Namely, fuel gas is cooled bycooling water inside the humidifying, chamber F.

[0074] Since cooling water is used to cool the heat generated in eachcell unit, the temperature of the cooling water supplied is bound to belower than that of the cell unit. If it is so arranged that the flow offuel gas moving inside the humidifying chamber is a counter flow withrespect to the flow of cooling water moving inside the humidifyingchamber, then saturated humidified fuel gas can be obtained from thehumidifying portion such that the temperature of the above-mentionedfuel gas is lower than the temperature of the cell unit and than thetemperature of a portion in the neighborhood of the humidified fuel gasoutlet on the plate C. For this reason, humidified fuel gas can besupplied to the fuel chamber without causing any water content in thehumidified fuel gas to be condensed.

[0075]FIG. 3(a) shows the results of measurements of temperatures in thehumidifying chamber F. The temperature of the fuel gas humidified bycooling water was approximately 74° C., while the temperature of aportion in the neighborhood of the humidified gas outlet (thetemperature of a header) was approximately 77° C. In the case of a priorart example shown in FIG. 10(a), the temperature of the fuel gashumidified by cooling water was approximately 79° C., while thetemperature of the header was approximately 78° C.; namely, thetemperature of the humidified fuel gas was higher than that of theheader, and therefore, the humidified fuel gas was cooled, therebycausing the humidified fuel gas to be cooled by the header, resulting inthe water content in the above-mentioned fuel gas to be condensed. FIGS.3(b) and 10(b) each show temperature distributions pertaining to apermeable film E.

[0076] Fuel gas humidified by cooling water inside the humidifyingchamber F is supplied to the above-mentioned fuel chamber C, and flowsdownward through a passage on the front side of the above-mentionedplate A and through a passage on the above-mentioned plate B. Coolingwater supplied through the cooling water inlet B5 on the plate (B)passes through a cooling water passage on each of the plates C, A, andB, in this order, and flows on the rear side of the plate, therebycooling each of the plates C, A, and C. Then the above-mentioned coolingwater passes through another cooling water passage (a return passage)and is discharged through the cooling water outlet B6 on the plate B.

[0077]FIG. 1 shows a case wherein cooling water is discharged to thenear side through the cooling water outlet B6 on the adjacent plate B.However, there is another case wherein cooling water, which progressessuccessively toward the rear of an integrally stacked fuel cell, flowsthrough each humidifying chamber F disposed between two adjacent cellunits, and is discharged through the other end of the fuel cell. On theplate B, humidified fuel gas flows downward through the front passagefacing the fuel chamber G as mentioned above, and cooling water flowsdownward through the rear passage facing the humidifying chamber F. Itfollows, therefore, that the flow of fuel gas moving inside the fuelchamber G is a co-flow with respect to flow of cooling water movinginside the humidifying chamber F (in the prior art example, these flowsare counter with respect to each other.)

[0078] Since it is so arranged, as mentioned above, the flow of fuel gasis a co-flow with respect to the flow of cooling water, the temperatureof the fuel gas at the outlet of the fuel chamber G becomes higher thanthe temperature of the fuel gas at the inlet of the fuel chamber G. Forthis reason, fuel gas is consumed at the outlet of the fuel chamber G,and therefore water condensation which would be caused by reduced flowvelocity can be prevented. As a result, stable fuel cell performance canbe achieved with no condensed water hampering the flow of fuel gas.

[0079] Now an explanation pertaining to oxidant gas will be made.Oxidant gas flowing in through the oxidant inlet B3 is supplied to theabove-mentioned oxidant chamber H. Namely, oxidant gas flows upwardthrough the passage facing the rear side of the plate A and through thepassage facing the rear side of the plate C, thus constituting a counterflow with respect to the above-mentioned cooling water flow.

[0080] As mentioned above, not only is humidified gas supplied to thefuel chamber G, but also oxidant gas is supplied to the oxidant chamberH, thereby causing the polymer electrolyte fuel cell to generateelectricity. In the course of the generation of electricity, the polymerelectrolyte membrane of each cell D is wetted by the water content inhumidified fuel gas to keep electric conductivity satisfactory, and thefuel cell main body is cooled by cooling water.

[0081]FIG. 4 shows the second embodiment of the polymer electrolyte fuelcell of the present invention, wherein the arrangement is the same asthat of the above-mentioned first embodiment, except that the locationsof the oxidant inlet B3 and of the oxidant outlet B 4 of the secondembodiment are reverse to those of the first embodiment. In the case ofthe second embodiment, fuel gas is supplied to each fuel chamber G afterbeing humidified by cooling water in the humidifying chamber F, just asin the case of the first embodiment. However, the second embodiment isdifferent from the first embodiment in that the flow of oxidant gasmoving inside the oxidant chamber H is a co-flow with respect to theflow of cooling water moving inside the oxidant chamber H. FIG. 5 is aschematic diagram showing flows of fuel gas, of oxidant gas, and ofcooling water, with component members integrally laminated.

[0082] Since it is so arranged, as mentioned above, that the flow ofoxidant gas moving inside the oxidant chamber H is a co-flow withrespect to the flow of cooling water moving inside the oxidant chamberH. the temperature at the outlet of the fuel chamber G becomes higher,and therefore, the water content can be prevented from being condensedat the outlet of the fuel chamber G. As a result, the fuel utilizationratio improves, as compared the above-mentioned first embodiment.

[0083]FIG. 6(a) shows the results of temperature measurements. Thetemperature at the fuel outlet turned out to be approximately 78° C.,which is higher than the fuel outlet temperature of approximately 76° C.in the case of the first embodiment. In this connection, the fuel outlettemperature in the prior art example as shown in FIG. 10(a) wasapproximately 74° C., FIG. 6(b) shows temperature distributions on apermeable film E.

[0084] With these embodiments taken into consideration, it is desirablethat the flow of humidified fuel gas flow moving inside the fuel chamberG, as well as the flow of oxidant gas moving inside the oxidant chamberH, is a parallel flow with respect to the flow of cooling water movinginside the humidifying chamber F.

[0085]FIG. 7 shows the results of an experiment carried out on fuelutilization ratios. In the case of the prior art example, the cellvoltage dropped when the fuel utilization ratio exceeded 40%, and thecell voltage drop rate increased with rising fuel utilization ratio,until the cell voltage degreased to approximately 50% when the fuelutilization ratio exceeded 90%. In contrast to the above, in the case ofthe polymer electrolyte fuel cells of the present invention, almost nocell voltage drop was observed in the range of high fuel utilizationratios.

[0086] Incidentally, in both of the above-described embodiments of thepresent invention, fuel gas is humidified in the humidifying chamber F.However, it may be so arranged that oxidant gas is humidified. In thiscase, fuel gas and oxidant gas may be replaced with each other tohumidify oxidant gas in the humidifying chamber F so that the polymerelectrolyte membrane of each of the above-mentioned cells D may bewetted when resulting humidified oxidant gas flows inside the oxidantgas chamber H. In the event oxidant gas is humidified as mentionedabove, the same effects can be obtained as in the case wherein fuel gasis humidified as mentioned above. Furthermore, it may be so arrangedthat both fuel gas and oxidant gas are humidified.

[0087] As described above, any polymer electrolyte fuel cell of thepresent invention is so arranged that the flow of fuel gas moving insidea fuel chamber, as well as the flow of oxidant gas moving inside anoxidant chamber, is a co-flow with respect to the flow of cooling watermoving inside a humidifying chamber. Therefore, the temperature at theoutlet of the fuel chamber or of the oxidant chamber is higher than thatat the inlet of the fuel chamber or of the oxidant chamber,respectively.

[0088] For this reason, fuel gas or oxidant gas is consumed at theoutlet of the fuel chamber or of the oxidant chamber, respectively, andconsequently, water condensation which would be caused by reduced flowvelocity can be prevented. As a result, stable fuel cell performance canbe achieved with no condensed water hampering the flow of fuel gas.

[0089] Furthermore, since it is so arranged that the flow of fuel gasmoving inside the humidifying chamber is a counter flow with respect tothe flow of cooling water moving inside the humidifying chamber,saturated humidified fuel gas can be obtained from the humidifyingchamber such that the temperature of the above-mentioned fuel gas islower than the temperatures of the cells and than the temperature of aportion in the neighborhood of the humidified fuel gas outlet. For thisreason, humidified fuel gas can be supplied to the fuel chamber withoutcausing any water content in the humidified fuel gas to be condensed.Furthermore, stable fuel cell performance can be achieved with nocondensed water hampering the flow of fuel gas.

What is claimed is:
 1. A polymer electrolyte fuel cell wherein a polymerelectrolyte membrane of a cell has an anode on one side and a cathode onthe other side; a fuel chamber with fuel gas flowing inside is providedon the anode side of said cell; an oxidant chamber with oxidant gasflowing inside is provided on the cathode side of said cell; said cell,said fuel chamber, and said oxidant chamber constitute a component cell;a plurality of said component cells are stacked together to constitute acell unit; a humidifying chamber with cooling water flowing inside isprovided between said cell units adjacent to each other, therebyhumidifying either fuel gas or oxidant gas, or both fuel gas and oxidantgas; and the flow of fuel gas moving inside said fuel chamber, as wellas the flow of oxidant gas moving inside said oxidant chamber, is aco-flow with respect to the flow of cooling water moving inside saidhumidifying chamber.
 2. A polymer electrolyte fuel cell wherein apolymer electrolyte membrane of a cell has an anode on one side and acathode on the other side; a fuel chamber with fuel gas flowing insideis provided on the anode side of said cell; an oxidant chamber withoxidant gas flowing inside is provided on the cathode side of said cell;said cell, said fuel chamber, and said oxidant chamber constitute acomponent cell; a plurality of said component cells are stacked togetherto constitute a cell unit; between said cell units adjacent to eachother is provided a humidifying chamber with fuel gas and cooling waterflowing inside to humidify fuel gas; fuel gas humidified by passingthrough said humidifying chamber humidifies said polymer electrolytemembrane; the flow of fuel gas moving inside said humidifying chamber isa counter flow with respect to the flow of cooling water moving insidesaid humidifying chamber; and the flow of fuel gas moving inside saidfuel chamber is a co-flow with respect to the flow of cooling watermoving inside said fuel chamber.
 3. A polymer electrolyte fuel cell asdefined in claim 1 , wherein the flow of oxidant gas moving inside saidoxidant chamber is a co-flow with respect to the flow of cooling watermoving inside said oxidant chamber.
 4. A polymer electrolyte fuel cellas defined in claim 2 or 3 , wherein fuel gas and oxidant gas arereplaced with each other to humidify oxidant gas in said humidifyingchamber.